Production method of rare earth magnet

Abstract

PROBLEM: To provide a production method of an anisotropic rare earth magnet capable of being enhanced in coercivity without adding a large amount of a rare metal such as Dy and Tb. MEANS FOR RESOLUTION: A production method of a rare earth magnet, comprising a step of bringing a compact obtained by applying hot working to impart anisotropy to a sintered body having a rare earth magnet composition into contact with a low-melting-point alloy melt containing a rare earth element.

The invention claimed is: 
     
       1. A production method of a rare earth magnet, comprising a step of bringing a compact obtained by applying hot working to impart anisotropy to a sintered body having a rare earth magnet composition into contact with a low-melting-point alloy melt containing a rare earth element, wherein said low-melting-point alloy melt containing a rare earth element is composed of an alloy having a melting point of less than 700° C. but not less than 480° C., and wherein the resulting rare earth magnet has a coercivity (Hc) of 17.5 kOe or greater at 300 k. 
     
     
       2. The production method as claimed in  claim 1 , wherein said low-melting-point alloy melt containing a rare earth element is composed of an alloy of at least one rare earth element selected from the group consisting of La, Ce, Pr and Nd and at least one metal selected from the group consisting of Fe, Co, Ni, Zn, Ga, Al, Au, Ag, In and Cu. 
     
     
       3. The production method as claimed in  claim 1 , wherein the rare earth element contained in said low-melting-point alloy melt is Nd or Pr. 
     
     
       4. The production method as claimed in  claim 1 , wherein the rare earth element contained in said low-melting-point alloy melt is Nd. 
     
     
       5. The production method as claimed in  claim 1 , wherein said low-melting-point alloy melt containing a rare earth element is NdAl. 
     
     
       6. The production method as claimed in  claim 1 , wherein said low-melting-point alloy melt containing a rare earth element is NdCu. 
     
     
       7. The production method as claimed in  claim 1 , wherein said sintered body is obtained by shaping a quenched body resulting from quenching of a molten alloy, by pressurization and sintering. 
     
     
       8. The production method as claimed in  claim 1 , wherein said sintered body is obtained by shaping a quenched body which has a nanocrystalline texture. 
     
     
       9. The production method as claimed in  claim 1 , wherein said sintered body is obtained by shaping a quenched body which is composed of an amorphous particle. 
     
     
       10. The production method as claimed in  claim 1 , wherein said hot working to impart anisotropy contains a step of unidirectionally compressing the sintered body at a temperature of 450° C. to less than 800° C. 
     
     
       11. The production method as claimed in  claim 1 , wherein the contacting step is performed at a temperature of 700° C. or less for 1 minute to less than 3 hours. 
     
     
       12. The production method as claimed in  claim 1 , wherein the contacting step is performed at a temperature of 580 to 700° C. for 10 minutes to less than 3 hours. 
     
     
       13. The production method as claimed in  claim 1 , wherein said sintered body has an Nd—Fe—Co—B-M composition wherein M is Ti, Zr, Cr, Mn, Nb, V, Mo, W, Ta, Si, Al, Ge, Ga, Cu, Ag or Au, Nd is from more than 12 at % to 35 at %, Nd:B (atomic fraction ratio) is from 1.5:1 to 3:1, Co is from 0 to 12 at %, M is from 0 to 3 at %, and the balance is Fe.